1. Field of the Invention
This present invention relates to a drive belt having a belt body which is made of a flexible material and a tensile reinforcement that extends in belt axial direction and which is surrounded by said belt body in sections at least to improve the tensile strength of the body in belt longitudinal direction wherein the tensile reinforcement is a carbon cord consisting of a plurality of twisted carbon fibers with a plurality of cavities between said fibers which are filled with a filler material in part at least.
2. Description of the Related Art
The invention also relates to a process for making a drive belt, which has a belt body made of a flexible material and carbon cords surrounded by said belt body in sections at least and extends in a belt longitudinal direction to improve the tensile strength of the body wherein the carbon cords consist of a plurality of carbon fibers which are twisted into a yarn and embedded into the curable flexible material forming the belt body.
Prior known from EP 0 841 500 B1 is a drive belt for transmitting a drive motion which comprises a belt body made of polyurethane as hardenable flexible material. A carbon cord is embedded in the belt body in a longitudinal direction thereof to provide a tensile reinforcement. Said carbon cord is formed by a plurality of twisted carbon fibers and dependent on the geometry of the carbon fibers and the production process has cavities between the fibers. Polyurethane is cast around said carbon cord with cavities to provide the belt body. Part of the polyurethane penetrates into said gaps of the carbon cord in the course of the casting process. The amount of polyurethane to be cast around the carbon cord is 0.20 mg, 0.24 mg or 0.28 mg per 1 mm cord volume even though larger amounts of polyurethane are considered advantageous. The drawback involved in this case is that the polyurethane contained inside the carbon fiber cavities makes the drive belt undesirably hard after curing which means that penetration of polyurethane into the carbon cord reduces the flexibility of the drive belt and increases the bending modulus thereof with the consequence that the carbon cord would be exposed to unacceptably severe loads as it turns around belt pulleys which might cause damages to (in particular ruptures of) the carbon cords and hence give rise to failures of the drive belt and a reduction of service life thereof.
It is an object of this present invention, therefore, to improve a drive belt and a process for making it in such a way that the flexibility and the service life of the belt will be increased after polyurethane has been poured around the carbon cords.